1. Field of the Invention
This invention relates to a vehicle body structure of a vehicle such as an automobile.
2. Description of the Related Art
In a vehicle body structure of a vehicle such as an automobile, particularly in a vehicle body front structure, it has been known that a cross member on the body side, which extends in the vehicle width direction of the vehicle, is installed between a pair of (side and left) side members extending in the longitudinal direction of the vehicle, and a cross member on the chassis side for mounting chassis parts is installed forwardly of the cross member on the body side.
As shown in FIGS. 5(a) and 5(b), for example, a front cross member (a cross member on the body side) 4 is installed between a pair of (right and lefty front side members 3A and 3B coupled to a pair of (right and left) front side sills 1A and 1B via braces 2A and 2B, and a plate-shaped sub-cross member (a cross member on the chassis side) 5, as a mounting member for a suspension or the like, is installed forwardly of the front cross member 4.
Rod-shaped reinforcing members 6 and 7 for reinforcing kickup portions (portions rising like mountains to allow passage of an exhaust pipe) of the front cross member 4 and the sub-cross member 5 are disposed, as shown in FIG. 5(a). Alternatively, the kickup portion of the front cross member 4 is reinforced with the rod-shaped reinforcing member 6, while the sub-cross member 5 is reinforced with a pair of (right and left) rod-shaped reinforcing members 8a and 8b which are installed, as diagonal bracings, at the pair of (right and left) front side members 3A and 3B, as shown in FIG. 5(b).
In these vehicle body front structures, the exhaust pipe (not shown) is set in place by a dedicated holding mechanism such as a bracket (see Japanese Unexamined Patent Publication No. 2001-164933 as a pertinent publication).
However, with the conventional vehicle body front structure, for example, that shown in FIG. 5(a), the reinforcing members 6 and 7 for the front cross member 4 and the sub-cross member 5 are not coupled together. Thus, as shown in FIG. 6(a), there are no bridges linking a front portion and a rear portion in a region indicated by the letter X in the drawing. This has posed the problem that in response to inputs transmitted from torsion or the like of the suspension or the body (see dotted arrows in the drawing), a phase difference occurs between the body side and the chassis side, resulting in a tendency toward a decline in rigidity. In order to ensure necessary rigidity (in order not to impair handleability, for example), therefore, it is necessary to set the wall thicknesses of the reinforcing members 6 and 7 at high values.
With the structure shown in FIG. 5(b), on the other hand, a backbone tunnel portion to be described later is not reinforced. Thus, as shown in FIG. 6(b), there has been the problem that in response to inputs transmitted from torsion or the like of the suspension or the body (see dotted arrows in the drawing), a region with low rigidity is present in a backbone tunnel portion indicated by the letter Y in the drawing, which serves as a support for the exhaust pipe or the like. In order to ensure necessary rigidity (in order not to impair handleability, for example), therefore, it is necessary to set the wall thicknesses of the reinforcing members 6, 8a and 8b at high values.
The present invention has been accomplished in light of the above-described problems with the earlier technologies. It is an object of the invention to provide a vehicle body structure equipped with a reinforcing member which can transmit forces to the body side and the chassis side in a well-balanced manner in response to inputs transmitted from torsion or the like of the suspension or the body, thereby ensuring efficient reinforcement.